Figure 10-28.-Two types of tie-rod anchorages for bulkheads.
of the tie rods are anchored by means of a channel
In the figure, the construction sequence begins
when the shore and bottom are first excavated to the
level of the long, sloping dotted line. The sheet piles
for the bulkhead and the anchorage are then driven.
The supporting piles for the tie rods are driven next,
after which the tie rods between the bulk and the
anchorage are set in place and the wales are bolted on.
The tie rods are prestressed lightly and uniformly, and
the backfilling then begins.
The first backfilling operation consists of placing
fill over the anchorage, out to the dotted line shown in
the plan. The turnbuckles on the tie rods are then set
to bring the bulkhead plumb, and the rest of the
backfill is worked out to the bulkhead. After the
backfilling is completed, the bottom outside the
bulkhead is dredged to the desired depth.
As mentioned earlier, wharfage structures allow
vessels to lie alongside for loading or unloading.
Moles and jetties are the most typical forms.
Figure 10-29.-Working drawings for a steel sheet pile
Moles and Jetties
A mole is simply a breakwater that serves as a
wharfage structure. The only difference is that its inner
or harbor face must be vertical and its top must
function as a deck. In a similar way, jetties also serve
as wharfage structures.
BELOW THE WATER TABLE
When construction is carried on below the
groundwater level, or when underwater structures like
seawalls, bridge piers, and the like, are erected, it is
usually necessary to temporarily keep the water out of
the construction area. This is typically done with well
points, cofferdams, or caissons.
Well points are long pipes thrust into the ground
down to the level at which the water must be excluded.